Cucurbituril-based hydrogels

Abstract

The invention provides a polymerizable composition and a hydrogel obtained or obtainable from the polymerizable composition. The polymerizable composition comprises cucurbituril and a first monomer having a guest for the cucurbituril, wherein the total monomer concentration, Cmon, within the polymerizable composition is at least 0.5 M. The composition may be an aqueous composition.

Description

RELATED APPLICATIONS[0001]The present case is related to GB 1617469.0 filed on 14 Oct. 2016 and GB 1708589.5 filed on 30 May 2017, the contents of both of which are hereby incorporated by reference in their entirety.FIELD OF THE INVENTION[0002]This invention relates to hydrogels based on cucurbituril cross-linked supramolecular networks, and methods for the preparation of such hydrogels from a polymerizable composition comprising cucurbituril and a polymerizable monomer having a guest for the cucurbituril.BACKGROUND[0003]Some of the present inventors have previously described supramolecular hydrogels that are based on the supramolecular complexation of the cucurbituril CB[8] with a polymer having guest functionality for CB[8].[0004]Appel et al. (J. Am. Chem. Soc. 2010, 132, 14251) describe hydrogels formed from the complexation of a composition comprising CB[8] and a low molecular weight polymer having guests for CB[8]. The supramolecular hydrogel has intra- and intermolecular non-c...

AI Technical Summary

Benefits of technology

[0014]The present inventors have found that these hydrogels have excellent mechanical physio-chemical properties, and these properties are improved compared with the cucurbituril hydrogels described previously by some of the inventors.

[0016]Using a polymerizable composition to prepare a hydrogel allows the use of the cucurbituril host and the cucurbituril guest at higher effective concentrations than previously reported. This therefore permits the formation of hydrogels having a higher degree of dynamic crosslinking. The formation of the supramolecular bonding is not affected by the issues seen from previous hydrogel preparations, where the supramolecular bonds are formed between polymers. In these prior art methods, a high level of non-covalent cross-linking is prevented by, amongst others, polymer chain entanglement, limited solubility of guest-functionalised polymers, low cucurbituril solubility in the polymer mixture, and the high viscosity of the starting polymer mixture.

[0018]The hydrogels of the invention may be prepared with a high water content, such as in the range 80 to 95 wt % water. These hydrogels nevertheless have great stretchability (for example, stretched up to 45 times their original length, such as 100 times their original length), and have very high fracture energies (for example, up to 2,100 J m−2). The hydrogels also have a high contractile stress (for example, up to 0.5 MPa), and they are capable of lifting objects having considerably greater mass than the hydrogel (for example, 500 times greater mass, such as 2,000 times greater mass). The hydrogels of the invention have high storage and loss moduli across a wide range of strain and frequency values (for example, 1,000 Pa or more, such as 10,000 Pa or more).

Problems solved by technology

The hydrogels previously reported by the inventors are useful, but their uses are limited by their relatively weak mechanical performance.

However, the use of increasing amounts of CB[8] is impeded by the limited solubility of this cucurbituril in compositions also comprising the polymers for the hydrogel network.

Such mixtures are not ideal, as they limit the types of structure than can be prepared, and there can be issues in manipulating the mixtures when used on a larger scale.

Most synthetic hydrogels are brittle and therefore poor candidates for mimicking biomaterials, regardless of their soft and wet nature, similar to that of biological tissues.

However, designing soft materials with high toughness and extreme stretchability is still a challenge.

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